This topic is probably going to have a lot of debate on it, but I'll cut to the point: not all R50 CVs are created equal, and one variation of them is prone to binding even in stock applications. I think this variation is undoubtedly the reason why there's such mixed opinions about the use of spacers and lift springs in regards to people busting CVs.
Let's be clear up front on some things:
Binding in this context is the inability for the CV to rotate smoothly, without restriction, when the suspension is at full droop (i.e., tire off the ground). We'll be talking about any severity of binding, as a CV shaft should always be able to rotate without binding.
Without a doubt, spacers can contribute to binding because they move the wheel hub downward, causing the normal operating angle of the shaft to increase. There's obviously an upper limit to the amount of spacers that can be used. For the sake of argument, let's say 2" is maximum permissible spacer lift amount for a non-SFD truck. (@fleurys, please weigh in on your opinion here since you've probably sold hundreds of your spacers and will have more insight than anyone here.)
No lift spring can cause binding, ever. The operating angle of a CV is strictly limited to the travel range of the wheel hub, which is directly limited to the compressed and extended lengths of the strut. The strut length is unaffected by a lift spring.
I'm making the claim about CVs because we observed it first-hand over the weekend while working on @Rockit's and @R50JR's trucks. On Rockit's truck, we installed a 3" SFD and replaced OME MDs with HDs on OME struts. On R50JR's, we didn't change anything about his suspension, but he has OME HDs on KYB struts. Adding my truck to the mix, I have a 3" SFD with OME HDs on KYB struts. For apples-to-apples, @Stpickens's has the same exact setup as Rockit's.
On Rockit's truck, we installed a pair of brand new Cardone 66-6185 (new, not remanufactured) CVs during the installation process. As we were starting to bolt everything back together, we noticed that both CVs were binding severely—guaranteed imminent failure. We debated whether it was the CV or the SFD, and I demonstrated that on my truck with a similar setup, I had no binding whatsoever. We eventually re-installed the original CVs and there was absolutely no binding. We also later confirmed that Stpicken's truck also had no binding.
After taking a few measurements, we confirmed that the OME strut is about 1" longer than a KYB strut, which basically has the effect of having a 1" spacer. We then determined that the new Cardone CV would begin to bind at 19°, whereas the original CV reached 24° with no binding at the maximum droop. That 5° also equated to 1" of travel, since we also measured the distance between the rotor and the ground.
On R50JR's truck, he had previously dealt with binding when he had a 1" spacer with the same KYB strut and OME HD spring. Even with the spacer removed, a very slight binding was still present. Coincidentally, the CV shaft shape looked exactly like the new Cardones. Neither of them looked like mine.
This is definitive evidence that R50 CVs are definitely not the spec'd the same. I've speculated that it's related to the fact that early model R50s and QX4 (99 and earlier) had struts that were longer than later models (00 and after), and this is confirmed by several manufacturers (including OME and Rancho) producing struts of different lengths. However, the length change could simply be attributed to the two different strut mounts (aftermarket mounts include a spacer so the same mount can be used for either application.) If perhaps the longer struts on early models equated to a longer droop relative to the newer models with shorter struts, it would suggest that older CVs may have had a higher maximum operating angle than newer. As such, it would then be plausible that aftermarket manufacturers used the new CV dimensions and then applied the parts to the full 96-04 model range. That's my best guess at the moment.
Also, we believe the issue is with the inner joint, not the outer because the binding occurred about every 120°, which coincides with the 3 bearing cups on the inner joint. As far as sensing binding, we put a screwdriver in the brake rotor slots and give it a slow turn. If there's binding, you'll feel it, but can also watch the front differential hangers shifting at the bushings.
What does it mean for us? Well it means that, potentially, for all the people who have had binding or have broken CVs when using spacers up to 2" tall, the issue may have actually been the CVs the whole time. As noted, there's slight binding on R50JR's with KYB struts and no spacers...not factoring the lift he's getting from his springs, this is an extremely common OE replacement setup that should have absolutely no binding at droop.
The main CV options are either OEM, aftermarket-new, or rebuilt. The problem here is that there's not usually any clear indicators of which is which, so there's not really good advice on which to buy. OEMs are presumably the best option to avoid this issue, but they can be very expensive ($550) though Nissan does have a "Value Advantage" part available ($150). Aftermarket ones are clearly less expensive, but if brand new Cardone ones aren't built to the same spec, you'd have to chance a rebuilt one being of one spec or another.
At this point, we might need a lot of community input to see if we can determine who has, or had, binding with which CV and which setup before we can know which CVs to avoid. We may need to rely on physical appearance of parts since some brandings or p/ns might not be visible. I'm thinking it's best to list the following:
CV brand and p/n (if known)
Any markings on the shaft
Your strut brand and p/n (stamped on the body)
Spacer height (if any)
Severity of binding on a 0-3 scale:
0 - no binding
1 - slight binding
2 - binding (can be overcome)
3 - severe binding (can be overcome with more force, or not at all)
A picture of shaft
Since strut p/ns vary by LH and RH side, it may help to include both if perhaps you've replaced struts and/or CVs separately and potentially have a mismatch (@notmeami).
Copy/Paste template...
CV Brand/PN:
Markings:
Strut Brand/PN:
Spacers:
Binding: